Geoff Roest

MS in Geosciences

San Francisco State University

QUASIGEOSTROPHIC DIAGNOSIS OF AN

EXPLOSIVELY DEVELOPING CYCLONE ALONG THE NORTHERN

CALIFORNIA COAST

OUTLINE

• Introduction

• Background

• Project Plan

• Rainfall, wind, and tornado data

• Qualitative Estimate of quasigeostrophic controls

• Quantitative Estimate of quasigeostrophic controls

• Hypotheses/objectives

CYCLOGENESIS

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

(Petterssen 1956)

• Major storm brought damaging winds and flooding rains

• Explosively developed prior to making landfall

• Developed eye-like feature, Thunderstorms

• At least 1 tornado

FEB. 19TH, 1993 STORM

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

FEB. 19TH, 1993 STORM

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

NWS BULLETINS FROM STORM

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

• Storms of this strength not unheard of in Eastern Pacific, but unusual

• Rapid development was noteworthy

• Significant impact on Northern California

FEB. 19TH, 1993 STORM

(Sanders and Gyakym 1980)

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

FROM SANDERS AND GYAKUM (1980)

• “Meteorological bomb” (aka “Explosively developing cyclone) – a cyclone that deepens at 12 mb in 12 hrs

• Feb 1993 storm – 13 mb in 14 hrs

• Climatology

• Often cold season, maritime events

• Downstream from mobile 500 mb trough and planetary wave trough

• Are largely baroclinic events

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

ADDITIONAL CRITERION FOR EXPLOSIVE CYCLOGENESIS

• Allen et al. (2010) discussed importance of relative pressure fall:

• Cyclone’s central pressure fall is important, but what if ambient atmospheric pressure decreases at same rate?

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

• Estimated forcing on the basis of quasigeostrophic diagnosis

• Findings

• Unusually strong baroclinicity

• Strong, persistant warm air advection

• Diabatic heating

• Sensible heating

• Latent heating

CASE STUDY OF EXPLOSIVE CYCLOGENESIS

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

Reed and Albright 1986

DESCRIPTION OF CYCLONE, EFFECTS

• Gathering rainfall and wind data from:

• National Climatic Data Center (NCDC)

• Western Region Climate Center (WRCC)

• National Weather Service statements and reports

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

• Reconstruct pressure field, height field, etc. using:

• Weather observations from land, buoys

• NCEP Reanalysis

• Tornadic thunderstorm

• Thermodynamic environment

• Shear environment

SYNOPTIC DISCUSSION OF CYCLONE

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

REASONS FOR DEVELOPMENT

• Quasigeostrophic theory –forcing mechanisms for vertical velocity

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

(Bluestein 1992, pp. 330)

REASONS FOR DEVELOPMENT

• Sutcliffe Petterssen Development Equation (Palmen and Newton, 1969, pp. 316-326)

• Can reconstruct development of storm using finite difference approximation on weather maps

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

• Diabatic heating

• Sensible heating (Allen et al. 2010)

• Latent heating (Reed et al. 1988)

• Static stability

• Lapse rates/lifted indices

• Moisture fluxes from ocean

PROJECT PLAN

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

(NOAA)

• Conditional symmetric instability (CSI) (Bennetts and Hoskins, 1979)

• Function of momentum and θe

• Conservation of momentum and entropy

• Not considered by static stability parameter

PROJECT PLAN

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

(Reed and Albright 1986)

• Hypotheses

• Dynamic environment supportive of explosive cyclogenesis

• Atmosphere was strongly conditionally unstable

• CSI contributed to cumulus convection

• Objectives

• Study extreme event using quasigeostrophic theory

• Estimate relative contribution of each term in Sutcliffe-Petterssen Development Equation to explosive development

INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

REFERENCES• Allen, J. T., A. B. Pezza, and M. T. Black, 2010: Explosive Cyclogenesis: A Global Climatology Comparing Multiple

Reanalyses. Journal of Climate, 23, 6468–6484.

• Bennetts, D. A., and B. J. Hoskins, 1979: Conditional symmetric instability - a possibleexplanation for frontal rainbands. Quarterly Journal of the Royal Meteorological Society ,105, 945–962.

• Holton, J. R., 1992: An Introduction to Dynamic Meteorology . 3rd ed. Academic Press, 511 pp.

• Monteverdi, J. P., E. Jan Null, Kathy L. Pagan, and Ernest Daghir, Explosively-developingcyclone with “eye”: Extratropical “hurricane” along the West Coast?

• National Weather Service, 1993: Northern and Central California Weather Summary . National Weather Service San Francisco, CA.

• National Weather Service, 1993: Storm Report for 2/19/93. National Weather ServiceEureka, CA.

• Palman, E., and C. W. Newton, 1969: Atmospheric circulation systems: their structure and physical interpretation . Vol. 13. International Geophysics Series, Academic Press, 624 pp.

• Petterssen, S., 1956: Weather Analysis and Forecasting . McGraw-Hill Publishing Company. Vol. 1. 428 pp.

• Reed, R. J., and M. D. Albright, 1986: A Case Study of Explosive Cyclogenesis in the Eastern Pacific. Monthly Weather Review, 114, 2297–2319.

• ——, M. D. Albright, A. J. Sammons, and P. Undén, 1988: The Role of Latent Heat Release in Explosive Cyclogenesis: Three Examples Based on ECMWF OperationalForecasts. Weather and Forecasting, 3, 217–229.

• Sanders, F., and J. R. Gyakum, 1980: Synoptic-Dynamic Climatology of the “Bomb”. Monthly Weather Review, 108, 1589–1606.

• Stumpf, C. J., 2012: A Comprehensive Survey of Buoyancy and Shear Parameters forCalifornia Tornadoes: 1951-2011. San Francisco State University, 167 pp.